Generally, cellular wireless communication systems are interference-limited. That is, different base stations (BSs) generate out-of-cell interference to neighboring mobile stations (MSs) using the same frequency channels. In addition, the fourth generation (4G) wireless communication systems, such as Long Term Evolution (LTE) Advanced, intend to achieve the frequency reuse factor of 1. Thus, interference mitigation techniques may be required for wireless communication.
Coordinated Multipoint (CoMP) transmission is envisioned to be an important component technology in third generation partnership project (3GPP) LTE-Advanced. In CoMP, inter-cell interference can be mitigated or eliminated by proper beamforming design. There are two major techniques in CoMP: joint processing and coordinated beamforming. In coordinated beamforming, the data stream for each mobile station (MS) is transmitted from a single base station (BS) node, and the beamformer design for each BS is coordinated among the cooperating BSs. Joint processing can achieve higher system throughput but may require the transmit data for different users to be available at each cooperating BS. In joint processing, selection of the base station cooperation sets and allocation of the user data can be crucial for the system performance.
The beamforming vector design has previously been used in a multicellular environment subject to Per-BS power constraint. In such a scenario, each BS is responsible for transmission to its own MSs, and no MS data is exchanged between different cells. Further, a zero-forcing scheme involving multiple BSs has been considered. For the zero-forcing scheme, the data for all the MSs in the cooperating cells are distributed among all the cooperating BSs. In addition, heuristic clustering methods for BS cooperation based on the distance between the BSs and MSs have also been used.